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From: Russell Standish <R.Standish.domain.name.hidden>

Date: Wed, 14 Jul 1999 12:23:09 +1000 (EST)

I was thinking some more on the physical laws issue, and on Wei Dai's

point on what measure to apply to different universes. The solution

given is to weight shorter strings over longer ones.

One way of thinking about this is to state that there are _no_ finite

strings at all in the everything world. Instead, the first n bits of a

string contain information, and the remainder are "don't care"

values. We also assume a uniform measure on all these infinite

strings. In this picture, worlds who are entirely specified by strings

with a smaller value of n will have higher measure than those with

larger n. The measure will fall off exponentially with n, in fact

precisely 2^{-n}, assuming the uniform measure above. This, then is

the universal measure sought by Wei Dai. Clearly, the everything

universe consists of all strings where we don't care what any bit

is. These have zero information, and measure = 1.

So, by the SSA (strong, weak, relative - doesn't matter in this case),

we should expect a Universe with low Kolmogorov complexity, but high

logical depth, which in essence says we should expect simple physical

laws, and a relatively long evolution producing concious entities. We

could call this the "minimum information principle".

In the Tegmark picture, he discusses mathematical structures, which

clearly should be preferred by the minimum information principle over

unstructured worlds. We should also expect to observe the most general

mathematical structure capable of supporting consciousness, as greater

generality => fewer axioms => less information. I have given arguments

in earlier posts why complex valued vector space with unitary

evolution operators (ie quantum mechanics as we know it) should be the

most general such mathematical structure, although at the time I didn't

know why the most general such structure would be preferred.

I disagree (for the moment at least) that the everything universes

should be restricted to programs on a universal turing machine. I

believe that it is information that is at the heart of the matter, and

that one can have information without computation (I'm happy to be

proven wrong if that is the case). However, the Schmidhueber picture

is at very minimum a useful metaphor, even if it turns out not to be

the whole story.

Cheers

----------------------------------------------------------------------------

Dr. Russell Standish Director

High Performance Computing Support Unit,

University of NSW Phone 9385 6967

Sydney 2052 Fax 9385 7123

Australia R.Standish.domain.name.hidden

Room 2075, Red Centre http://parallel.hpc.unsw.edu.au/rks

----------------------------------------------------------------------------

Received on Tue Jul 13 1999 - 19:21:27 PDT

Date: Wed, 14 Jul 1999 12:23:09 +1000 (EST)

I was thinking some more on the physical laws issue, and on Wei Dai's

point on what measure to apply to different universes. The solution

given is to weight shorter strings over longer ones.

One way of thinking about this is to state that there are _no_ finite

strings at all in the everything world. Instead, the first n bits of a

string contain information, and the remainder are "don't care"

values. We also assume a uniform measure on all these infinite

strings. In this picture, worlds who are entirely specified by strings

with a smaller value of n will have higher measure than those with

larger n. The measure will fall off exponentially with n, in fact

precisely 2^{-n}, assuming the uniform measure above. This, then is

the universal measure sought by Wei Dai. Clearly, the everything

universe consists of all strings where we don't care what any bit

is. These have zero information, and measure = 1.

So, by the SSA (strong, weak, relative - doesn't matter in this case),

we should expect a Universe with low Kolmogorov complexity, but high

logical depth, which in essence says we should expect simple physical

laws, and a relatively long evolution producing concious entities. We

could call this the "minimum information principle".

In the Tegmark picture, he discusses mathematical structures, which

clearly should be preferred by the minimum information principle over

unstructured worlds. We should also expect to observe the most general

mathematical structure capable of supporting consciousness, as greater

generality => fewer axioms => less information. I have given arguments

in earlier posts why complex valued vector space with unitary

evolution operators (ie quantum mechanics as we know it) should be the

most general such mathematical structure, although at the time I didn't

know why the most general such structure would be preferred.

I disagree (for the moment at least) that the everything universes

should be restricted to programs on a universal turing machine. I

believe that it is information that is at the heart of the matter, and

that one can have information without computation (I'm happy to be

proven wrong if that is the case). However, the Schmidhueber picture

is at very minimum a useful metaphor, even if it turns out not to be

the whole story.

Cheers

----------------------------------------------------------------------------

Dr. Russell Standish Director

High Performance Computing Support Unit,

University of NSW Phone 9385 6967

Sydney 2052 Fax 9385 7123

Australia R.Standish.domain.name.hidden

Room 2075, Red Centre http://parallel.hpc.unsw.edu.au/rks

----------------------------------------------------------------------------

Received on Tue Jul 13 1999 - 19:21:27 PDT

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